Heat hardening fluid coke compactions



Feb. 6, 1962 F. M. STEPHENS, JR. ET AL 3,020,210

HEAT HARDENING FLUID COKE COMPACTIONS Filed Feb. 24, 1955 ELECTRICHEATER GAS Frank M. Stevens, Jr. Howard C. Renken Small Dunhom 8rThomcls Inventors Patent Attorney United States Pate 3,020,210 HARDENTNGFLUID COKE COMPACTIONS Jr., and Howard C. Renken, Colummesneassignments, to Esso Company, Linden, N.J., a

This invention relates to improvements in the thermal heat hardening offluid coke compactions. More particularly it relates to a process ofthis nature wherein the compactions are heat hardened by being immersedin a dense turbulent fluidized bed of coke particles.

There has recently been developed an improved process known as the fluidcoking process for the production of fluid coke and the thermalconversion of heavy hydrocarbon oils to lighter fractions, e.g., seeSerial No. 375,088 filed August 19, 1953, now Patent No. 2,881,130,granted April 7, 1959. For completeness the process is described infurther detail below although it should be understood that the fluidcoking process itself is no part of this invention.

The fluid coking unit consists basically of a reaction vessel or cokerand a heater or burner vessel. In a typical operation the heavy oil tobe processed is injected into the reaction vessel containing a dense,turbulent, fluidized bed of hot inert solid particles, preferably cokeparticles. A transfer line or staged reactors can be employed. Uniformtemperature exists in the coking bed. Uniform mixing in the bed resultsin virtually isothermal conditions and effects instantaneousdistribution of the feed stock. In the reaction zone the feed stock ispartially vaporized and partially cracked. Product vapors are removedfrom the coking vessel and sent to a fractionator for the recovery ofgas and light distillates therefrom. Any heavy bottoms is usuallyreturned to the coking vessel. The coke produced in the process remainsin the bed coated on the solid particles. Stripping steam is injectedinto the stripper to remove oil from the coke particles prior to thepassage of the coke to the burner.

The heat for carrying out the endothermic coking re action is generatedin the burner vessel, usually but not necessarily separate. A stream ofcoke is thus transferred from the reactor to the burner vessel, such asa transfer line or fluid bed burner, employing a standpipe and risersystem; air being supplied to the riser for conveying the solids to theburner. Sufficient coke or added carbonaceous matter is burned in theburning vessel to bring the solids therein up to a temperaturesuflicient to maintain the system in heat balance. The burner solids aremaintained at a higher temperature than the solids in the reactor. About5% of coke, based on the feed, is burned for this purpose. This mayamount to approximately 15% to 30% of the coke made in the process. Thenet coke production, which represents the coke makes less the cokeburned, is withdrawn.

Heavy hydrocarbon oil feeds suitable for the coking process includeheavy crudes, atmospheric and crude vacuum bottoms, pitch, asphalt,other heavy hydrocarbon petroleum residua or mixtures thereof. Typicallysuch feeds can have an initial boiling point of about 700 F. or higher,an A.P.I. gravity of about to 20, and a Conradsou carbon residue contentof about to 40 wt. percent. (As to Conradson carbon residue see A.S.T.M.Test D-189-41.)

A problem in the marketing of the fluid coke product is the small sizeof the particles, i.e., about 60-90 wt. percent, are in the range of 20to 80 mesh. The production of substantially larger particles isinconsistent with satisfactory operation of the fluid bed. On the otherhand in- 3,020,210 Patented Feb. 6, 1962 ice dustrial requirementsforcoke often necessitate particles having a diameter of about at least Vsinch to 1 inch.

Compactions of the indicated size made from fluid coke are of severaltypes, i.e., pellets, extrusions, and briquettes. All have in common theutilization of an agglutinating carbonaceous substance as a binder.

The agglutinating carbonaceous binder substances that can be utilizedinclude suitable hydrocarbon binders, such as asphalt and .other heavypetroleum residues, aromatic tars, e.g. vacuum reduced thermal tars,heavy ends of coal tar, such as coal tar pitches having a minimumsoftening point of about 100 C., and heavy ends from the cokingoperation, i.e., 1050 F. material. Some specific examples of the bindersare Elk Basin residuum (160 F. softening point), Enjay 160 Asphalt andHawkins coker bottoms. These substances are utilized in an amount ofabout 5 to 20 wt. percent, based on the coke charge and preferably 10 to15 wt. percent. v

The natural fluid coke can be used to make briquettes, but the' behaviorof briquettes during heating and the strength of the final products areimproved by grinding the coke to produce finer particles. If the coke isto be pelletized, it must be ground. 7

Pellets in general are prepared by grinding the fluid coke to give afines fraction, e.g., minus 100 mesh, and mixing the coke with about 10%binder. The binder is ground either separately or in mixtures with thecoke. Enjay 160 asphalt can be ground by itself.- Elk Basin and Hawkinscoker bottoms became too sticky, even when mixed with coke, to enablethem to be ground at normal temperatures. Consequently, artificialcooling is used to grind mixtures of these asphalts and coke.

These mixtures (about to coke and 10% to 15 asphalt) are ground in aball mill with about 25% water. Ice is used to hold the temperaturebelow-75 F. The ground mixture is filtered and the product containingabout 25% water is passed through a screen to break up the lumps. Thesepellets are then charged to a rotating drum for balling so as to subjectthem to a rolling motion on a horizontally rotated surface.

The briquettes are prepared by admixture of the fluid coke as is orpartially ground with about 10% of an agglutinating carbonaceoussubstance at a temperature of about 250% to 300 F. The mixture isbriquetted in a hydraulic press at a pressure of about 2100 to 9600p.s.i. Roll presses such as those commonly employed to make briquettesfrom coal and other materials can be used. Such machines are describedin the Chemical Engineering article Agglomeration, Chemical EngineeringOctober 1951, page 161 on, especially pp. 163-65.

The machines are equipped with steam-heated mixers when coal briquettesare made with tar binders. The hot mililttures of coal and binder passdirectly to the pressing re s.

These compactions require heat hardening at tempera-- tures of above 900F. to decompose the binder to a carbonaceous residue and to produceadequate strength and cohesion. Treating at these temperatures, however,because of the melting of the binder material results in the deformationof the compactions and also adherence to each other. In addition ofcourse elevated temperatures tend to oxidize the compactionsundesirably.

This invention provides an improved method of thermally hardening thecompactions of fluid coke which- The method comprises heat treating thecompactions by immersing them in. a dense,

turbulent, fluidized bed of coke particles, preferably fluid cokeparticles, at atemperature in the range of about 900 F. preferably 1200to 1800 F. The time of treatment is conventionally in the range of 15minutes to 2- hours. The fluid coke particles of the bed can be utilizedas is, without grinding.

The eflicacy of this very specific method of heat treating thecompactions is surprising in that other heat treating methods testedgive distinctly inferior results. Thus more than substituting one methodof heat treating for another is involved. The reducing atmospherepresent in a body of coke particles maintained at this temperature alsocontributes to the desired results.

The dense, turbulent, fluidized bed of coke can be brought up totemperature by means of external heating and/or partial combustion ofthe coke. Thus, the coke in the fluid bed can be partially heated byindirect heat exchange and partially burned by a fluidiz ing gas such asair. Conversely all of the heat can be supplied by burning the coke inan auxiliary burner and recycling the hot coke to the compactionstreating zone. Fluidizing gas such as air or nitrogen can be employeddepending upon whether combustion of the coke is required to supply thenecessary temperature. A superficial fluidizing velocity of the gas inthe range of 0.5 to 4 ft./ sec. can be employed. Air slides can beutilized to convey the compactions through the bed.

Several stages of fluid bed reactors can be utilized where it is desiredto bring compactions slowly up to a temperature as in the case ofmoisture containing pellets. The cooling of the briquettes can beaccomplished by a wide variety of methods, such as by the use of waterquench in the form of a mist, bedding them in cold fluid coke or bypassing a gas such as cooled combustion gas over them.

Two types of tests are employed to evaluate the physical properties ofcompactions:

(1) Tumbling.This is used as an indication of abrasion or dustingresistance. The test is carried out in a porcelain jar 7 /2 inches indiameter and 7 /2 inches in length. The jar is rotated at 70 r.p.m. for2400 revolutions. The size distribution is then measured.

(2) Drop test.This is carried out on the compactious and may be a 220volt Globar furnace using electrical resistance heaters 22.

To heat the formed briquettes a wire basket is provided which is shownat 24 and is partially broken away to show briquettes 26 in the basket.The basket has an open top and has a smaller diameter than the diameterof the heater 10. The wire basket is provided with a handle 28 so thatthe basket may be submerged in the fluidized bed as shown in the drawingand may be removed from the fluidized bed after the desired heating.

The following example demonstrates the invention.

EXAMPLE Briquettes were prepared from fluid coke and 10 wt. percent ElkBasin residuum binder by molding at a pressure of about 9000 p.s.i. Themixture which was briquetted in the. particular case consisted of:

Constituent: Parts by weight Natural fluid coke Ground fluid coke (87%minus 200 mesh) 45 Elk Basin asphalt 10 This mixture, at roomtemperature, was pressed into briquettes by use of an automatichydraulic press operating at two tons pressure or about 9000 p.s.i. Thegreen briquettes were about inch in diameter and one inch tall. Theyweighed about 9.2 grams each. It was not necessary to dry thesebriquettes because they contained no water.

These briquettes were then immersed in a dense, turbulent fluidized bedof coke, the coke being predominantly in the normal fluid coke range.The bed was brought up to temperature in a fluid bed reactor by acombination of an electrically heated jacket and partial combustion withthe fluidizing air. The heating was carried up to 900 to 1800 F. but thebriquettes were immersed when the bed was at 500 F. The baked briquetteswere tested by the beforementioned tumbling and drop tests. The resultsare presented below in the table.

T he effect of baking conditions on the quality of briquettes Wt. ofMate- Wt. of Plus 4- Wt. oi Minus Time to Wt. oi Baked Wt. of Bririal(Minus 20- Mosh Material 4-Mesh Mate- Volatile Reach Briquettes, quettesAfter Mesh) Abraded After Dropping rial Produced Combustible Final Temp.of Final Percent of Tumbling, Per- From Bri- Tumbled Briin Dropping,Matter, Per Heating Fluid, F. Temp, Green Bricent of Green quettes inquettes, Per- Percent 01 cent of Baked Min. quettes Briquettes Tumbling,Percent of Green Green Bri- Briquettes cent of Green Briquottcs quettosBriquettes recovered from the tumbling test. They are dropped 33 /3 feetonto a steel plate. The fragments are screened to provide a quantativemeasure of degradation.

The FEGURE represents one form of apparatus adapted to carry out theprocess of the present invention.

Referring now to the drawing, the reference character 10 designates aheater containing a fluidized bed of finely divided solids 12 which arepreferably fluid coke particles having a level indicated at 14. Theheater or furnace 10 has a conical bottom 16 into the apex of which isintroduced a fluidizing gas through line 18 to maintain the cokeparticles as a dense turbulent fluidized bed by flowing upwardlytherethrough. If it is desired to supply additional heat to thefluidized bed 12, the fluidizing gas may be air which is used topartially burn the fluid coke particles in the fluidized bed. Thefurnace or heater it can be heated by any conventional indirect heatexchange means or it may be placed in another furnace.

One relatively simple way of heating the heater 10 is by electrical heatand this is diagrammatically shown at 22 The table shows the heatingconditions employed. All of the green briquettes were immersed when thefluid coke under fluidization was at 500 F. The first vertical columnshows the temperatures that were attained in the fluidized coke bed whenthe various specimens were removed. The second vertical column in thetable shows the time that was employed to heat from 500 F. to thetemperature shown in the first column. The numbers in the fifth andsixth vertical columns reflect the strength of the products obtained byheating under the conditions of time and temperature shown in columns 1and 2. All of the products are considered satisfactory as far asstrength is concerned. That is, the maximum degradation during thetumbling test was 9.3%, as shown in the fifth vertical column and mostresults were below this figure. A sample of high grade foundry coke,which is an article of commerce, lost 8.2% when subjected to the sametumble test.

The only method that consistently produced briquettes that wereconsidered acceptable was by heating in fluid Conditions in fluid cokerreactor Broad Preferred Range Range Temperature, F 850-1, 200 900-1, 000Pressure Atmospheres 110 1. 2 Superficial Velocity of Fluidizing Gas,Fla/Sec- 0. 2-10 0. 5-4 Coke Circulation (Solids/Oil Ratio) 2-30 7-15The advantages of this invention are apparent to those skilled in theart. Strong compactions are produced by heat hardening the latter in amanner which prevents their normal deformation. In addition a reducingatmosphere is made available during this heat hardening treatment whichprevents the excessive oxidation and consequent yield degradation of thecompactions. 1

It is to be understood that this invention is not limited to thespecific examples which have been offered merely as illustrations andthat modifications may be made without departing from the spirit of theinvention.

What is claimed is:

1. In the thermal heat hardening of compactions of fluid coke particlesmade by a fluidized coking process with an agglutinatiug hydrocarbonbinder substance at heat hardening temperatures at which temperaturesthe compactions normally tend to deform and oxidize, the improvementwhich comprises immersing the fluid coke compaction in a dense,turbulent, fluidized bed of coke particles maintained at heat hardeningtemperature to decompose said binder to a carbonaceous residue toproduce adequate strength whereby deformation and excessive oxidation ofsaid compaction are prevented, and withdrawing the thus heat hardenedcomp-action from said fluidized bed.

2. The process of claim 1 in which the heat hardening temperature is inthe range of 900 to 1 800 F. and the compactions treated contain about 5to 20 wt. percent binder based on the fluid coke.

3. A process according to claim 1 wherein said heat hardening step ismaintained under reducing conditions.

4. The process of claim 1 in which the coke particles in the dense,turbulent, fluidized bed are fluid coke particles.

5. The process of claim 4 in which the compactions being treated arebriquettes prepared by molding fluid coke with an agglutinatingcarbonaceous substance in a briquetting press.

6. A process for heat hardening compactions of coke particles made in afluid coking process with a high boiling agglutinating hydrocarbonbinder in an amount of about 5 to 20% based on said fluid cokeparticles, which comprises heating the compaction at a heat hardeningtemperature between about 900 F. and 1800= F. for 15 minutes to 2 hoursto decompose the binder to a carbonaceous residue and to improve thestrength and cohesion of the coke particles by immersing the fluid cokecompaction in a hot dense, turbulent fluidized bed of coke particlesmaintained at heat hardening temperature and removing the heatedcompaction from said fluidized bed.

7. A process according to claim 6 wherein the compaction being treatedis a briquette prepared by subjecting the mixture of said fluid cokeparticles and agglutinating binder to a pressure of between about 2100and 9600 psi.

8. A process according to claim 6 wherein at least part of said fluidcoke particles are subjected to grinding before being heat hardened.

9. A process according to claim 6 wherein at least part of said fluidcoke particles are subjected to grinding before being mixed with saidagglutinating binder.

10. A process according to claim. 6 wherein said heat hardening step ismaintained under reducing conditions.

11. A process according to claim 6 wherein the coke particles of saiddense turbulent fluidized bed comprise fluid coke particles.

References Cited in the file of this patent UNITED STATES PATENTS1,655,728 Johnston et a1 Ian. 10, 1928 1,948,472 Loebell et a1. Feb. 20,1934 2,105,832 Becker Jan. 18, 1938 2,314,641 Wolf Mar. 23, 19432,511,088 Whaley June 13, 1950 2,560,357 Martin et al. July 10, 19512,661,326 Stillman Dec. 1, 1953 2,719,779 Bray et al. Oct. 4, 19552,729,598 Garbo Jan. 3, 1956 2,776,935 Jahnig et al. Ian. 8, 19572,825,679 Baum Mar. 4, 1958 2,843,533 Smith et a1 July 15, 1958 FOREIGNPATENTS 1,062,128 France Apr. 20, 1954 1,087,226 France Aug. 18, 1954UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,02021O February 6, 1962 Frank M. Stephens Jr. et a1.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

In the sheet of drawing, bottom of the sheet, name of flrst lnventor,for "Frank M. Stevens, Jr. read Frank M. Stephens, Jr.

Signed and sealed this 5th day of June 1962.

SEAL) ,ttest:

RNEST w. SWIDER DAVID L ,ttesting Officer Commissioner of Patents

1. IN THE THERMAL HEAT HARDENING OF COMPACTIONS OF FLUID COKE PARTICLESMADE BY A FLUIDIZED COKING PROCESS WITH AN AGGLUTINATING HYDROCARBONBINDER SUBSTANCE AT HEAT HARDENING TEMPERATURES AT WHICH TEMPERATURESTHE COMPACTIONS NORMALLY TEND TO DEFORM AND OXIDIZE, THE IMPROVEMENTWHICH COMPRISES IMMERSING THE FLUID COKE COMPACTION IN A DENSE,TRUBULENT, FLUIDIZED BED OF COKE PARTTICLES MAINTAINED AT HEAT HARDENINGTEMPERATURE TO DECOMPOSE SAID BINDER TO A CARBONACEOUS RESIDUE TOPRODUCE ADEQUATE STRENGTH WHEREBY DEFORMATION AND EXCESSIVE OXIDATION OFSAID COMPACTION ARE PREVENTED, AND WITHDRAWING THE THUS HARDENEDCOMPACTION FROM SAID FLUIDIZED BED.